This application is based on and incorporates herein by reference Japanese Patent Application No. 2001-320806 filed Oct. 18, 2001.
The present invention relates to a rotary electric machine used as motors or power generators in vehicles, aircraft, industrial tools and the like where compactness and high efficiency are highly required.
Motors and generators as rotary electric machine used in vehicles are greatly needed to be compact, light weight and high performance. Magnetic flux governs the performance of the motor and the generator. To attain compactness and increase of magnetic flux, a rotor having a Lundell-type magnetic field core is used. This core comprises a boss press-fit around a rotary shaft, disc portions extending from the boss and claw-shaped magnetic poles connected to the disc portions. In this core, magnetic flux is generated by a magnetic field winding which is wound in a simple centralized winding, and the magnetic flux is generated in parallel to magnetic circuits which are formed with respective claw-shaped magnetic poles. Thus, it realizes high magnetizing ampere-turns at respective claw-shaped magnetic poles.
However, when using the Lundell-type rotor, in case the rotor is determined to a certain diameter, a diameter of the boss governing quantity of magnetic flux is not able to be enlarged so much in order to acquire necessary radial thickness of claw-shaped magnetic poles and quantity of the magnetic field winding. As a result, the magnetic flux easily saturates in the boss, thereby limiting improvement of the output. In addition, as the magnetic field core comprising claw-shaped magnetic poles is a mass as a whole, eddy currents develop in the surface of the claw-shaped magnetic poles when the magnetic flux fluctuates. As a result, it experiences more magnetic pole losses than general layered magnetic poles.
It is therefore an object of the present invention to provide a rotary electric machine, which attains high performance and minimizes loss of magnetic flux.
According to the present invention, a rotary machine has a stator having an annular stator core which is wound with multi-phase windings and a rotor disposed radially inside the stator core to generate rotating magnetic fields. The rotor has a rotor shaft, a boss, disc portions, cylindrical parts and a magnetic field winding. The boss is press-fit around the rotor shaft. The disc portions extend radially from an outer periphery of the boss. The cylindrical parts are disposed radially outside the boss in connecting with the disc portions and are continuous in a circumferential direction. The magnetic field winding is disposed between the boss and the cylindrical parts. The rotor has a shape or structure to give a cyclic change of magneto-resistance corresponding to a cycle of an electric angle 2 xcfx80 of the multi-phase windings at the outer peripheries of the cylindrical parts. Hereby the cylindrical parts are used as magnetic poles instead of Lundell-type claw-shaped poles. Therefore, when centrifugal forces act on the rotor, tensile stresses to widen the whole cylindrical parts radially outward develop instead of immense bending moments which affect the claw-shaped poles formerly. Thus, the magnetic poles formed on the rotor are equipped with certain resistance to centrifugal forces.
In addition, the magnetic poles are able to be made thinner than the claw-shaped poles to carry the same quantity of magnetic flux as the claw-shaped poles do because the whole portions of the cylindrical parts lead the magnetic flux. Therefore, when the field winding is wound in the same condition, the diameter of the boss is enlarged, which results in increase of the quantity of magnetic flux passing through the boss which governs output performance eventually, and thus, performance of the rotary electric machine is improved.